//C16:16.5:variadic.c -- variadic marco.
#include <stdio.h>
#include <math.h>
#define PR(X, ...) printf("Message " #X  ": " __VA_ARGS__)

int main(void)
{
    double x = 48;
    double y;

    y = sqrt(x);
    PR(1, " x = %g\n", x);
    PR(2, "x = %.2f, y = %.4f\n", x, y);
}